Sample scoring can be generated by three different hidden models:
the latent variable (LV) model, the composite variable (CV) model,
and the unobserved variable(UV) model.
The LV model consists in a confirmatory factor analysis (CFA) with one
factor and specific error variances [1]}:
\( Y_j = \lambda _j F + E_j \quad \mathrm {with}\quad \mathrm {var}(F) = 1\, \, \, \mathrm {and} \, \, \, \mathrm {var}(E_j) = \psi _j\) 
